Wake evolution and boundary layer interactions in large-scale wind farms

With the rapid expansion of wind energy, wind farms are increasingly being developed in clustered configurations. Consequently, it is essential to assess the spatiotemporal evolution of wake effects within large wind farm cluster (WFC) and their impact on power generation performance. In this study, the spatiotemporal evolution of wakes and their influence on power generation performance were investigated using a mesoscale meteorological model coupled with a wind farm parameterization scheme. The Jiuquan Wind Power Base, situated in Gansu Province’s Hexi Corridor, China, was chosen as the study area because of its significant contribution to national wind energy generation. The results indicate that wind profiles exhibit clear diurnal variations: enhanced vertical mixing during the day produces a relatively uniform wind field, while at night the wind field shows strong vertical wind shear with higher wind speeds at hub height. Wake effects reduce near-surface wind speeds, producing wakes that are weaker but vertically extensive during the day, and stronger but more confined at night, thereby moderating vertical wind shear near the surface. Under stable conditions, the average wind speed deficit at hub height reaches 33%, with the wake extending up to 450 m; under unstable conditions, the deficit decreases to 16%, and the wake reaches nearly 1000 m. Wake-induced turbulence increases turbulent kinetic energy (TKE) within and above the rotor-swept region, especially at night, while TKE below the rotor decreases due to reduced shear. Inter-farm wake interactions lead to an average capacity factor loss of 56% for the WFC, with the most pronounced losses occurring under low to moderate wind speeds and particularly under stable atmosphere.